Answer
$$2 \pi$$
Work Step by Step
We need to integrate the integral to compute the volume.
We have:
$$Area =\pi (R^2- r^2)=\pi (4-4x)$$
Now,
$$Volume = \pi \times \int_{0}^{1} (4-4x) dx \\ = \pi [4x-2x^2]_{0}^{1} \\= \pi (4-2-0+0) \\=2 \pi$$
